Method of frosting the inner surface of alpha glass bulb



T. NARUSE Sept. 6, 1932.

METHOD OF FROSTING THE INNER SURFACE OF A GLASS BULF Filed Sept. 6, 1950INVENTOR. TING-ruse A TTORNEYS.

Patented Sept. 6, 1932 UNITED STATES PATENT OFFICE TOMISABURO NABUSE, OFUCEIYAMASHITA-GHO, KOJ'IMAGHI-KU, TOKYO, JAPAN METHOD OF FROSTING THEINNER SURFACE OF A GLASS BULB Application filed September 6, 1930,Serial No. 480,278, and in Japan September 20, 1929.

This invention relates to a method offrosting a portion of the innersurface of a glass bulb of an electric lamp; consisting in firstinjecting in the bulb a special etching liquid through a narrow tube andthereupon extracting said liquid therefrom; said liquid containing apowder selected from a group consisting of powdered starch andcornflour, which acts to give cohesiveness to the liquid, to stir theliquid when it is injected in the bulb, whereby a sharp, clear, dividingline, between the frosted and transparent parts of the bulb and thesmooth even surface of the frosted part are obtained.

More particularly, the purpose of the invention is to obtain by the aidof a special etching, liquid and quickly the uniform edge or dividingline and the smooth even surface of the frosted part, wherebybeautifullooking lamps can be made.

Now, if the method of frosting a glass bulb by pouring in and suckingout a corrosive liquid without a powder through a narrow tube beemployed in frosting only a part, not the whole, of a glass bulb,inconveniences are chiefly caused by the excessive fluidity of theliquid.

Because of this fluidity, the liquid causes vortex motion while beingpouredinto the bulb through a narrow tube and numerous wavelets areproduced on the surface of the liquid, causing a zigzag edge of thefrosted surface, or the liquid splashes and stains such part as isdesired to be left transparent.

And now, if a glass bulb is frosted by pouring in and sucking out anetching liquid which contains liquid state mucilage or other viscousmaterials, say viscous starch, through a narrow tube; then abovementioned zigzag line will be more smooth, but

on-account of the stronger etching action in the 'lower part of the bulbthan at the upper part of it, caused by the considerable time which isnecessary in pouring and sucking out the liquid, that is to say, thebottom of the bulb keeps longer contact with the liquid than theupperpart, consequently Vertical lines or horizontal circular lines are pro-1 'duced on the frosted part. 5.0 This invention aims. at securingperfect finish of the frosted part of an electric bulb, by removing suchdefects as are experienced when a corrosive liquid without a powder isused, namely:

(1) first, decreasing the excessive fluidity of the liquid, to lessenthe possibility of the wavelets being produced by the vortex motion ofthe liquid, and to prevent the liquid from splashing;

(2) secondly, accelerating the mixing proc- 6o xissugf the liquid whenit is poured into the (3) thirdly, in order to lessen the strongcorroding .or etching action at the lower part of the bulb where theliquid, after being poured in, remains longest in contact with the bulb;this method employs an etching liquid containing some powder (e. g.starch, corn flour), which affects the etching action of the liquid veryslightly and the specific gravit of which is somewhat greater than that0 any other elements contained therein.

In order that the invention may be more fully understood, a practicalexample is given below: 7

Parts Hydrogen fluoride 38 Ammonium fluoride 38 Sulphuric acid 5 Water15 Now, the desired etching liquid can be ob tained first by mixingtogether the above mentioned elements and then by mixing into itAmerican flour whose quantity is 20% of the mixture. It would beneedless to say that the elements should vary according to the nature ofthe glass, and it has been found that 30 parts each of hydrogen fluorideand ammonium fluoride are eflective. And as to ,the relation between thespecific gravity of the liquid and that of the powder it is enough ifthe powder be heavy enough to sink easily in the liquid.

Two examples of a suitable apparatus are shown in the accompanyingdrawing.

Fig. 1 shows in elevation an apparatus for this method, partly insection.

Fig. 2 shows other example for this method.

According to Figs. 1 and 2, above mentioned corrosive liquid is injectedand sucked out of the bulb (1) by one or two narrow tubes (2). In theapparatus shown by Figure 1 the liquid (5) is saved in the tank (3) andto inject the liquidin the bulb push the'piston (4) downwards as thearrow (at) shows, and to suck the liquid out of the bulb pull the piston(4i) upwards as the arrow ((1') shows. In the apparatus shown by Fig. 2the liquid (5) is saved in the tank (3) and when the tank is situated atthe position that the liquid level is placed above the bulb (1) the cock(6) is opened, then the liquid in- 1' ected in the bulb, until theliquid level in the bulb reaches to the required height. After corrosionis finished, the tank is lowered until all the liquid in the bulb issucked out.

As regards the advantages of the said invention, among others, ispointed out the possibility of obtaining a sharp, clear line between thetransparent and the frosted part, in as much as the vortex motion of theliquid can be lessened to the limit even when 1t is poured into andsucked out of the glass bulb under quicker action than when the etchingliquid without powder is used, to say nothing of the ease of obtainingthe beautiful finish of the work, for the powder mixed in the liquidhelps to stir up the liquid completely, because greater momentum isgiven to the powder while being poured into'the glass on account of itsgreater specific gravity than that of any other element containedtherein, and at the same time the said powder sinks or settles easilyand lessens the corroding action at the lower part of the bulb to someextent and thus saves the frosted surface from ugly wavelets. 7

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare whatI claim is z- 1. A method of frosting a portion of the inner surface ofa glass bulb of an electric lamp; consisting in first injecting in thebulb liquid to alter the etching action in the a special etching liquidthrough a narrow tube and thereupon extracting said liquid therefrom;said liquid containing a powdered material selected from a groupconsisting of starch and cornfiour, which acts to give cohesiveness tothe liquid,'whereby a sharp, clear, dividing line, between the frostedand transparent parts of the bulb is obtained said 'powdered materialsettling in the etching parts where the material has settled.

2. A method of'frosting a portion of the inner surface of a glass bulbof an electric lamp; consisting in first injecting in the bulb a specialetching liquid through a narrow tube and thereupon extracting saidliquid therefrom; said liquid containing a powder selected from agroiipconsisting of starch and cornflour, which acts to give cohesivenessanswers

